Do anyone have written documents that identify what percentage of questions must be different from a previous test when developing test questions. Same question for writing remedial test questions?

e61369 - Why are you writing another test? Did you use CRTD when developing the first test? If so, are you substituting questions that did not fall within the guidelines?

Sorry for so many questions, but just trying to understand how you developed your first test and why you need to redevelop.

Here is a great article on CRTD. If you develop and maintain your tests with this method, you should never have to rewrite your tests.
http://www.cambridge.org/elt/crlt/sample/introduction.htm

Hope this helps.